As the battle for Mosul draws to a close, the war on extremist ideas must ramp up

What does the defeat of ISIL in one of its traditional strongholds mean for the terror group prospects?

Iraqi civilians flee the ISIL-controlled old city of Mosul. Martyn Aim / Getty Images

Slowly but surely, ISIL’s control over territory in Iraq and Syria is coming to an end. But what does that mean for the future of radical extremists in the region and for Middle East social cohesion more generally?

There are a few things that ought to be said from the outset. The first is that caution over suggestions that ISIL will suddenly disappear should not detract from the success of the Iraqi forces in defeating the group in different parts of the country. Far too many, it seems, were utterly dismissive about the possibility that Iraqi forces might be able to dislodge ISIL. In reality, they were quite successful. Yes, there are legitimate questions to be asked about the anti-Sunni sectarianism of certain Shia militias in Iraq, but that should not detract from the campaign successes.

The second thing that must be admitted is that the end of ISIL’s control over certain parts of territory in Iraq and Syria does not mean the end of its rule entirely. They will exist for some time; but certainly, there is good cause for optimism about the end of its territorial expansion and, indeed, ISIL’s contraction.

Thirdly, the end of territorial control does not spell the end of ISIL as a movement. It means the transformation of the group, a morphing of it, rather than its disappearance. That morphing might result in more than one offshoot. The nature of such radical movements in the past has always included a tendency towards splintering. How those divisions might play out is uncertain, but it is certainly something to watch.

Fourthly, ISIL’s ideology, apart from the group itself, is not about to die. On the contrary, even while it was unable to maintain its territorial integrity for more than a short while, its ideological attraction has staying power. The reality is that there is now a very real and potent memory that extremists can and will rely on. It will no longer be about truth and facts, if indeed it ever was. It will be about the myth that was the so-called "Islamic State". The actual experience of people who lived under ISIL rule will be forgotten.

As time goes on, the failure of the ISIL experience will be recast and revised, so that ISIL can pretend and falsify its own record in aid of recruitment. The recruits will dream of re-establishing a mythic condition that never really existed in the way they will think it did and they may carry out atrocities in support of that aim.

Which brings us to the fifth thing to keep in mind, that while Al Qaeda and other radical movements will still be deeply disturbing threats, particularly in Yemen, ISIL will also be a terrorist group with a potent message. Battling that ideology, and reducing the political and social conditions that increase the likelihood of recruitment successes are still high priorities.

All of that is the negative aspect of the battle at hand. There is also a positive one. The world is facing a massive challenge with pluralism in diverse societies. That is seen all over the globe, and ISIL links to that phenomenon. ISIL trades in the most brutal form of identity politics that we have seen in a long time.

But it is not enough that we look at how ISIL deals with minorities. It is necessary that we prioritise how we, the majority, engage with pluralism and diversity, whether as Arabs in this region, or as westerners in Europe and North America. That is a big challenge and one that in the past decade or so in the West, people have been lax in addressing constructively and effectively. It is only, alas, when crisis hits that they consider the best, most cohesive and broadest model for engaging difference. Well, crisis has hit and the effects are clear for us all to see. Sectarianism, Islamophobia, anti-Christian bigotry, extremist identity politics, lack of appropriate political and civil space, these are all symptoms of societies that have failed to sufficiently deal with the challenges of pluralism. As we move forward, whether in the Arab world or elsewhere, we must realise that seriously engaging with that set of challenges is a first priority for today, tomorrow and many years undoubtedly to come.

Dr HA Hellyer is a senior non-resident fellow at the Atlantic Council in Washington and the Royal United Services Institute in ­London